It is known to receive circularly polarised signals using a patch antenna. Such an antenna comprises a dielectric substrate having parallel upper and lower planar surfaces. Typically the upper surface bears a conductive layer with a rectangular outline and the lower surface has another conductive layer acting as a ground plane. According to the feed configuration, the antenna is sensitive to circularly polarised radiation reaching the antenna from a direction generally above and perpendicular to the upper surface.
Another antenna for circularly polarised radiation is a turnstile antenna. A turnstile antenna typically comprises a set of two dipole antennas which are aligned in a common plane at right angles to each other and which are fed 90 degrees out-of-phase. When mounted with its axis vertical, a turnstile antenna provides an almost omnidirectional circularly polarised radiation pattern with a vertically directed maximum. It is known to add a reflector underneath the dipole elements of a vertical axis turnstile antenna. The antenna pattern can be altered by changing the distance between the reflector and the dipole elements.
It is an object of this invention to provide an improved antenna for receiving and/or transmitting polarised radiation.